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Leopard Shark (Triakis semifasciata) and Spotted Gully Shark (T. megalopterus) Fact Sheet: Reproduction & Development

Leopard Shark (Triakis semifasciata) and Spotted Gully Shark (T. megalopterus) Fact Sheet

Courtship

Leopard shark

  • Mating
    • Believed to occur shortly after pupping (Ackerman 1971, Talent 1985, Ebert 2003)
    • Little known about courtship and mating behavior in the wild; only reported once (Smith 2005), as of 2015
    • Some reports from managed care settings (Ackerman 1971)
  • Mating system
    • Evidence of multiple paternity (two sires in about 36% of litters in La Jolla, California); some females may mate with multiple males (Nosal et al. 2013b)
      • All- or mostly-female aggregations may limit exposure to coercion to mate with many males (Nosal et al. 2013b)

Spotted gully shark

  • Mating
    • Unknown
  • Mating system
    • Unknown

Reproduction

Shark and ray reproduction

Leopard shark

  • General
    • Livebearing; young develop inside the mother without placenta (“aplacental viviparity,” or “yolk sac viviparous reproduction”) (Castro 2011)
    • Annual reproductive cycle reported; confirmation may be needed (Castro 2011; Nosal et al. 2013b)
    • “No comprehensive reproductive studies on leopard sharks…some observations in the literature are difficult to reconcile…” (Castro 2011)
  • Breeding
    • Sexual maturity (Ackerman 1971; Kusher et al. 1992; Castro 2011; Carlisle et al. 2015)
      • Females: 105-135 cm (3.4-4.4 ft) TL (about 10-15 years old)
      • Males: 100-105 cm (3.3-3.4 ft) TL (about 7-13 years)
    • Mating season
      • Said to occur from April-May, or perhaps summer; not well understood (Smith 2005; Smith and Horeczko 2008; Castro 2011; Nosal et al. 2014)
      • For females, given an annual reproductive cycle, mating and fertilization thought to occur within 1-2 months of giving birth (Ebert 2003; Nosal et al. 2013b)
    • Nursery areas
      • Shallow bays of California (Ebert 2003; Castro 2011)

Spotted gully shark

  • General
    • Young develop inside the mother without placenta (“aplacental viviparity,” or “yolk sac viviparous reproduction”) (Smale and Goosen 1999)
    • Reproductive cycle seems to be 2-3 years, but little known about how much time between pregnancies (Smale and Goosen 1999)
  • Breeding
    • Sexual maturity (Smale and Goosen 1999; Booth et al. 2011; Ebert et al. 2013; Maduna et al. 2017)
      • Females: about 140-150 cm TL (or 15 years old)
      • Males: 125-135 cm TL (possibly 11 years or older)
        • Smallest mature males found by Soekoe (2016) were 142 cm (4.7 ft) TL
      • This species needs to grow to a large body size before reaching sexual maturity, even compared to the leopard shark
    • Mating season
      • Probably occurs from October to early December (spring/summer in the Southern Hemisphere) (Smale and Goosen 1999)

Gestation and Birth

Leopard shark

  • Pregnancy
    • Gestation: 10-12 months (Ebert 2003; Castro 2011)
      • Resting period follows in some individuals; few individuals inactive after a breeding season (Ebert and Ebert 2005)
    • Pregnant females at some aggregation sites spend substantial daytime hours in warm water (behavioral thermoregulation), possibly to accelerate embryonic development and/or another reproductive benefit (e.g., refuge from males) (Hight and Lowe 2007; Nosal et al. 2013b; Nosal et al. 2014)
      • Females give birth elsewhere (Nosal et al. 2014)
  • Birth
    • Season of birth
      • Occurs in spring and summer (Castro 2011)
      • April-June (Nosal et al. 2013b), possibly as early as March (Love 1996) and extending through July (Smith and Horeczko 2008)
        • Many pups born in April and May (Carlisle et al. 2007)
      • Geographical variation
        • Southern California: probably May and June, with reports as late as September in San Diego Bay (Smith 2005; Carlisle et al. 2015 citing Eigenmann 1891)
        • Central and northern California: March-September; peak in April and May (Ackerman 1971)
    • Habitats where born
      • Southern California: thought to be the surf zone and sheltered coves along the open coast (Smith 2001; Ebert 2003; Hight and Lowe 2007; Nosal et al. 2013a); observations of birth over sand/mud, as well (Smith 2001)
      • Northern California
        • “Females generally give birth in shallow protected habitats, often over sand or mudflats” (Carlisle et al. 2015); bays and estuaries (Ebert 2003)
        • In some locations, also observed giving birth over eelgrass (Ebert 2003; Ebert and Ebert 2005)
    • Litter/brood size: often reported as 6-36 pups (Castro 2011), although Ebert and Ebert (2005) state 1-37 and Ebert et al. (2013) state 4-37
      • Generally, litter size (number of young per breeding season) increases with female body size (length); common among triakid and mustelid sharks (Ebert and Ebert 2005; Nosal et al. 2013b)
    • Size at birth
      • Variable reports; about 17-23 cm (7-9 in) (Ackerman 1971; Kusher et al. 1992; Love 1996; Ebert and Ebert 2005; Smith and Horeczko 2008)

Spotted gully shark

  • Pregnancy
    • Gestation: 19-21 months (Smale and Goosen 1999)
      • Followed by a 2-3 month resting period
  • Birth
    • Season of birth
      • Not well known; August-September in some locations (Soekoe 2016)
      • According to Soekoe (2016), may be influenced by regional water temperatures, with cool-temperate populations giving birth 3-6 months earlier than warm-temperate populations (however, small sample sizes)
    • Litter/brood size: 5-15 pups, possibly 16; average litter size: 8-10 (Smale and Goosen 1999; Ebert et al. 2013; Soekoe 2016)
    • Size at birth: 40-45 cm (16-18 in) TL (Smale and Goosen 1999)
      • Soekoe (2016) reports 40-50 cm (16-20) TL
    • Smallest free-swimming individuals (neonates/newborns)
      • Over 55 cm (1.8 ft) TL (Smale and Goosen 1999)
      • 37 cm (1.2 ft) TL (Soekoe 2016)

Life Stages

Leopard shark

  • Newborn
    • Bays and estuaries are important nursery areas for populations in central and northern California (Carlisle et al. 2015)
    • Surf zone and sheltered coves may be nursery areas for populations in southern California (little remaining estuarine habitat along the mainland) (Ebert 2003, Hight and Lowe 2007, Nosal et al. 2013a)
    • Newborns may move about in a loosely organized group; may be a means of protection or finding food (Ackerman 1971; Ebert 2003)
    • Feed on small prey; Ebert and Ebert (2005) noted that fish eggs are an important prey item for young sharks in Humboldt Bay
  • Juvenile
    • Females grow about 2.4 cm (1 in) each year; males about 1.9 cm (0.75 in) (Kusher et al. 1992; Ebert 2003; Smith and Horeczko 2008)
    • Feed on crustaceans, clam siphons, innkeeper worms, and fish eggs (Smith and Horeczko 2008)
    • Feeding structures adaptable to be able to capture a variety of prey (Lowry et al. 2007)
    • Use inshore nursery areas, especially in central California (Carlisle et al. 2007)
    • Males and females may be found in the same area; sex ratios close to 1:1 (Carlisle et al. 2007)
  • Adult
    • Feed on fish and invertebrates (Smith and Horeczko 2008)

Longevity

Leopard shark

  • In the wild
    • At least 25 years, possibly up to 30 years (Castro 2011; Carlisle et al. 2015); influenced by gender (Kusher et al. 1992)
      • Males: at least 24 years of age
      • Females: at least 20 years of age
  • In managed care
    • Not reported; may be longer than in the wild (Andrew P. Nosal, personal communication)

Spotted gully shark

  • In the wild
    • Oldest sharks reported by Soekoe (2016): 25-30 years
  • In managed care
    • Maximum recorded age: 25 years (Booth et al. 2011)

Mortality and Health

Leopard shark

  • Predators (Ebert 1991; Hight and Lowe 2007; Nosal et al. 2014; Russo 2015)
    • California sea lion, Zalophus californianus
    • Sevengill shark, Notorynchus cepedianus, and likely other large sharks
      • From San Francisco Bay: small sevengills known to eat newborns (Russo 2015)
    • Caspian Terns, Hydroprogne caspia, and Great Blue Herons, Ardea herodias, observed preying on young sharks (Russo 2015)
    • Humans (Carlisle et al. 2015)
  • Illness and diseases (non-comprehensive list)
    • Brain infection, possibly caused by a fungus that spreads during low salinity conditions (such as after rainy seasons in northern California) and/or pollution; little known (Rogers 2017); also see Russo (2015)
      • Leopard shark die-offs in northern California in 2017, 2011, 2006, and reported as long ago as 1967 (Russo 2015; Rogers 2017)
    • Potentially harmful mercury concentrations detected in developing leopard shark embryos; contaminants transferred from mother to embryo (van Hees and Ebert 2017)
    • Near agricultural areas, pesticides and chemicals can accumulate in sediments, potentially impacting the health of leopard sharks (Carlisle et al. 2007)
    • First discovery in a non-bony fish: intracellular bacteria Chlamydiales, which is associated with the disease epitheliocystis (an infectious disease of the gills; causes necrosis)

Spotted gully shark

  • Survival rates
    • Juvenile survival is very important in the population dynamics of this species (Booth et al. 2011)
    • Booth et al. (2011) state that this species has a low natural mortality rate, but this may require further investigation
  • Predators
    • Sevengill shark, Notorynchus cepedianus (Ebert 1991)
    • Possibly other sharks; confirmation needed
    • Humans (Compagno 2009; Best et al. 2013; Best and Attwood 2013)

Sharks Have Predators, Too

Leopard shark being hunted by a male California sea lion

A male California sea lion hunting a leopard shark.

The fatty livers and developing eggs of pregnant female leopard sharks are thought to be a calorie-rich food source for some sea lion populations in California.

Image credit: © J.J. Newman. All rights reserved. Used with permission from the artist.

Image location: Catalina Island, California

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